Our solar system formed 4.5 billion years ago in an extremely chaotic environment and has evolved significantly over that time. What we see today is an organized inner solar system with four very different terrestrial planets. Join Dr. Shahar for an exploration of these planets as we try to understand their diversity. By analyzing rocks we can hold in our hands today and conducting experiments in the laboratory, we can probe which processes and conditions the terrestrial planets experienced billions of years ago.

Anat Shahar

Anat Shahar is pioneering a field that blends isotope geochemistry with high-pressure experiments to examine planetary cores and the Solar System’s formation, prior to planet formation, and how the planets formed and differentiated. Stable isotope geochemistry is the study of how physical and chemical processes can cause isotopes—atoms of an element with different numbers of neutrons-- to separate (called isotopic fractionation). Experimental petrology is a lab-based approach to increasing the pressure and temperature of materials to simulate conditions in the interior Earth or other planetary bodies.

Rocks and meteorites consist of isotopes that contain chemical fingerprints of long-gone eras. The lighter isotopes, with fewer neutrons, partially separate from heavier isotopes (fractionation). The different ratios of these isotopes can reveal the physical and chemical changes these materials have undergone.

Comparing seismic measurements and information on materials, researchers know that Earth’s outer core is not pure iron and nickel; something lighter is there. One candidate is silicon, the most abundant element in the crust. Shahar and her colleagues developed a way to test the silicon hypothesis. They developed lab techniques to define how isotopes of silicon and iron separate between metals characteristic of the core and silicate of the mantle under Earth-forming high pressures and temperatures. The results were compared with isotopes found in rocks on Earth and the most primitive meteorites called chondrites. Chondrites contain tiny grains of dust from the period when the Solar System began to coalesce. They found that the core could contain as much as 6% silicon by weight.

Shahar received her B.S. and M. Eng. from Cornell University in geological engineering and geological sciences respectively. She received her Ph. D. in geochemistry from UCLA. Before becoming a staff scientist in 2009 she was a Carnegie postdoctoral fellow.